Retinal light-damage is studied at low-to-moderate intensities (5 to 500 lux) in albino and pigmented rats. Methods include light-microscopy, electroretinography, visual pigment assays and pupillometry. Present and proposed work centers around two hypotheses: 1) Light-adaptation and light-damage lie on a continuum of light-effects on the retina; and (2) photoreceptors, normally anaerobic in light, cannot long tolerate this metabolically inefficient state and therefore die in constant light. These hypotheses will be tested in several ways: 1) Rats, light-adapted in (what are called) "normal" ways, will be assayed for rhodopsin content, ERG threshold and retinal integrity. The same lighting regimes will be (are being) extended into the damaging" domain. The idea is to show that "normal" light-adaptation leads smoothly into damage. 2) Various means for assaying the metabolic states of rats, treated as in 1) above, will be employed. These methods include measurement of rates of protein synthesis and receptor turnover as well as utilization of dyes and radioactive labels which signal the metabolic states of cells.